Publishing their findings in the Journal of Neuroscience, researchers from the University of Calgary believe that probiotics work to alter the communication between the immune system and the brain, decreasing symptoms of fatigue, depression, and social withdrawal that are usually seen in chronic inflammatory diseases, like rheumatoid arthritis and inflammatory bowel disease. So far, researchers have examined a reduction in these symptoms within mice that had liver inflammation.

Most of the processes of our gastrointestinal tract are carried out by microbiota, a mass of microorganisms that regulate digestion and our immune system health. Probiotics, consisting of many different cultures of live bacteria and yeasts, can help microbiota maintain digestive health when introduced into the gastrointestinal tract. Previous studies have also found thatprobiotics has positive effects on mood and cognition, but up until now, how probiotics interact with the brain has been relatively unknown. Researchers are finding that the answer is linked to the immune system.

For the study, researchers examined how mice with liver inflammation responded to receiving probiotics or a placebo. In order to measure how the mice responded to probiotics, researchers examined the length of time the mice engaged in social behaviors as opposed to the amount of time spent alone. In order to measure changes to brain function, researchers relied on previous research, which concluded that inflammatory disease often comes with an increased production of the inflammatory signaling molecule tumor necrosis factor alpha (TNF-α). They then measured levels of TNF-α in the blood as well as the number of activated immune cells in the brain.

Overall, they found that the mice who had received the probiotics spent longer amounts of time engaging in social behaviors than those who were fed a placebo. Mice who were administered probiotics were also found to have lower levels of TNF-α, with fewer immune cells in the brain being activated when compared to those in the control group. Interestingly enough, though, the probiotics did not appear to reduce the severity of liver inflammation, just its behavioral symptoms.

The researchers believe that their findings give evidence to the previous theory that probiotics help reduce behavioral symptoms by changing communication between the immune system and the brain. “In the setting of inflammatory disease, eating probiotics may be a novel way to improve the disease-associated symptoms that negatively impact the lives of patients,” study author Mark Swain said in a recent press release.

Other scientists within the field believe that this study has wider implications that extend to the possibility of treatment remedies. Keith Kelly, an immunophysiologist at the University of Illinois, believes the study has a lot of potential. “The global implication of these data is that the gut microbiome can perhaps be manipulated to not only regulate immunity but also to regulate the neural circuitry that affects behavior,” he said.